Oprah Winfrey’s new cable network, OWN, will be under the microscope from the first minute it hits the air today at noon.

But the network will not hit its stride until next fall — after Winfrey wraps her daytime talk show, “Oprah,” and becomes the fulltime head of the channel that she says she’s been dreaming of for 20 years. A lot of ink has been spilled trying to talk about OWN’s debut while at the same time keeping expectations down — at least until the boss herself arrives later this year.

As you watch the new channel — the most ambitious TV launch in years — keep these things in mind:

1.) Reruns of “Oprah” — 25 years worth of reruns — will eventually serve as the backbone of the new network.

But the reruns won’t start until September.

And when they finally do get on the air, you may not recognize them. They’ll be edited from the originals and repackaged as theme shows — Oprah and celebrities, Oprah’s book club, etc., according to sources.

The library of Winfrey’s past shows — nearly 5,000 hours in all — is one of the most highly valued properties in TV.

She first promised them back in 2000 to the Oxygen network, in which she was an investor. But then, she took them back — “my babies,” she called them in an interview — when she didn’t like the way the new cable network was going.

Right now, she is contractually prohibited from re-airing her daytime show until after it completes its syndicated run (the last “Oprah” airs Sept. 9). But after that, she is free to rerun the material from her old show any way she pleases.

The reruns (which will be given a new name) are expected to air in daytime –though nothing’s definite yet.

Because there is so much material there, it is expected that the repackaged shows will be aired a lot as the new network builds up its own stock of original shows.

The reruns are breathing room for the network to find its feet.

2.) Don’t expect to see Oprah hosting her new OWN show until late this year.

Yes, Winfrey will appear in a “behind-the-scenes” show documenting the final season of her famous daytime show — and she’ll introduce all eight episodes of “Oprah Presents Master Class” (in which celebs like Simon Cowell and Jay-Z tell all about their lives and work).

But her prime-time showcase, “Oprah’s Next Chapter” — in which she’ll travel around the world with her fabulous friends — can’t begin until September at the earliest. And it may take some time after that before the famous perfectionist is ready to go on TV with a new show.

Sooner or later, it will air two-to-three times each week in prime time, sources say.

3.) The first months of programming on OWN will be about creating the network itself.

They even have one TV show — “Your OWN Show: Oprah’s Search For The Next TV Star” — about making a TV show.

Produced by “Survivor” creator Mark Burnett and premiering next Friday night, 10 finalists will compete to host a show on OWN.

The finalists include a formerly homeless man who’s now a minister (Dr. Tony Roach from Abilene, Texas); an LA TV reporter (KTLA’s Elizabeth Espinosa); and a gay comedian from West Hollywood (Ryan O’Connor). Winfrey will appear on the show occasionally.

4.) You’ll have to wait until Monday to see much of OWN’s new shows.

This weekend will be filled with “sneak peeks” and specially crafted Oprah introductions.

Only snippets of shows like Gayle King’s new morning show, a sex-talk show hosted by Dr. Laura Berman and a cooking show with Cristina Ferrare will air this weekend. Twelve OWN shows — including sneak previews of “Kidnapped By the Kids” and “Searching For” — will premiere throughout this month.

5.) The summer of 2011 will be a turning point for Oprah.

She tapes her final original “Oprah” episode in May.

The show will air repeats throughout the summer, ending in September,

But, essentially, after the last week in May, she becomes a cable TV personality.

During the summer months, she will either throw herself into making new shows for her to star in beginning later this year — or she will take off, delaying the moment she starts appearing regularly on her own channel.